1. Field of the Invention
The invention relates to a multi-washer and to a method of cleaning gasses, particularly of raw synthesis gas from the gasification of municipal and other wastes which contain carbon particles, hydrogen sulphide, water vapor and volatile heavy metals.
2. Description of Related Art
According to the prior art, in order to clean contaminated industrial gases of all types, but also in order to improve the quality of utility gases, the gas to be cleaned is passed through a plurality of horizontally mounted substance exchangers, which are loaded with a wash liquid. These washers have the purpose of removing the materials contained in the gas, such for example as CO.sub.2, CO, NO.sub.x, H.sub.2 S or also solid impurities such as dusts from the gas flow by means of the wash liquid. A plurality of wash liquids are known, which as a rule physically and/or chemically bind, if necessary absorb or adsorb, only one specific toxic material.
The document JP 55-22238 demonstrates such a device for cleaning gases, in which there are located within a substantially horizontally lying container a plurality of wash regions, through which the gas to be cleaned is passed upwards and downwards in a meandering fashion.
The individual wash regions have substance exchangers stacked horizontally one above the other at defined spacings in the form of wash trays consisting of packings with filling members, which are sprayed with wash liquid on one side, on their outer side lying on top. These are thus wash towers, combined into a single pressure vessel, disposed in a horizontal alignment, and through which the gas passes vertically, as is conventional for individual tower scrubbers.
These known columnar washing systems have a series of disadvantages when applied to the cleaning of synthesis gases from waste gasification. Due to the horizontal layering of the individual substance exchangers, the cleaning liquid running off the substance exchangers and charged with materials runs into the further wash trays lying underneath. Particularly in the case of lumpy and adhesive contents such as carbon particles and sulphur, this leads in a short time to clogging and stoppage of the wash trays.
Because of these disadvantages, washers are used which eliminate the above-described substance exchangers and instead blow the gas to be cleaned merely through a spray mist of the cleaning liquid, so-called spray washing. A disadvantage of these spray washers is that the contact surface between gas and liquid is small compared to that of the substance exchangers, and therefore a reduced cleaning effect is achieved. The document EP 0 249 400 A1 illustrates such a washer, in which a horizontally-disposed pressure container is divided into individual zones. In these zones a spray mist of cleaning liquid is produced, through which the gas is passed. The spray mist is then precipitated on inclined droplet collectors and collected in a common sump, which likewise tends to clog due to sedimentation of lumpy and adhesive contained materials.